Increasingly, resources such as heavy crude oils, tar sands, shale oils, and coal are being utilized as hydrocarbon sources due to decreasing availability of easily accessed light sweet crude oil reservoirs. These resources are disadvantaged relative to light sweet crude oils, often containing significant amounts of sulfur, nitrogen, metals, and heavy hydrocarbon fractions including residue and asphaltenes. The disadvantaged crudes typically require a considerable amount of upgrading in order to obtain useful hydrocarbon products therefrom.
Numerous catalysts have been developed for catalytically hydrocracking and hydrotreating disadvantaged hydrocarbon feedstocks. Typically, these catalysts contain a Group VIB or Group VIII metal supported on a carrier formed of alumina, silica, or alumina-silica. Such catalysts are commonly sulfided to activate the catalyst, either before contacting the catalyst with a disadvantaged hydrocarbon feed or in situ with the disadvantaged hydrocarbon feed.
Applicants have discovered that a bimetallic or polymetallic thiometallate or selenometallate material is an exceptionally good catalyst for upgrading disadvantaged hydrocarbon feedstocks, particularly for converting all or substantially all heavy fractions such as residue and asphaltenes in the feedstock to lighter fractions while forming little or no coke. In particular, Applicants have discovered that bimetallic or polymetallic tetrathiomolybdates, tetrathiotungstates, and tetrathiovanadates and their tetraseleno-analogs are especially effective for hydrocracking disadvantaged hydrocarbon feedstocks to upgrade the feedstocks.
Catalysts used for hydrocracking and/or hydrotreating crudes or crude fractions are known to have higher catalytic activity as the surface area of the active component of the catalyst increases—more molecules in the crude or crude fraction may interact with surface of the active component. The surface area of an unsupported catalyst typically increases with decreasing catalyst particle size.
Ammonium and alkylammonium thiometallates have been used as precursors to produce metal sulfides. For example, tetralkylammonium thiomolybdate, tetralkylammonium thiotungstate, and ammonium thiomolybdate precursor compounds have been treated at temperatures of above 350° C. to thermally decompose the precursor compounds to produce MoS2 and WS2 disulfides having predicable stoichoimetry that have a high surface area and show substantial hydrodesulfurization and hydrodenitrogenation catalytic activity. Ammonium thiometallates have also been used as precursors to produce bimetallic compounds in an organic solvent. For example, copper thiometallates and copper selenometallates have been produced using a solvothermal method by reacting (NH4)2MoS4, (NH4)2WS4, (PPh4)2MoSe4, or (PPh4)2WSe4 with copper borofluoride salts in organic solvents at temperatures of 110° C. or above in an autoclave at autogenous pressures. Iron-molybdenum sulfide compounds have been produced by dissolving (NH4)2MoS4 in an organic chelating solution of diethylenetriamine (dien) and slowly adding an iron salt in a 10% aqueous dien solution to precipitate a hydrodenitrogenation catalyst precursor. The precursor is thermally decomposed to remove organic ligand constituents and sulfactivate the catalyst. Copper thiomolybdates containing oxygen have been produced from ammonium tetrathiomolybdates and a copper salt by mixing aqueous solutions of reactants CuSO45H2O and M2I-MoS4 (MI=NH4+, Et4N+, or Na+) and (NH4)2MoS4 in the presence of oxygen. Such methods are not known to produce bimetallic or polymetallic tetrathiometallates containing little or no oxygen and having a high surface area and/or a particle size distribution having a mean or median particle size of at least 50 nm but less than 5 μm.
Bimetallic tetrathiometallate or tetraselenometallate materials containing little or no oxygen and having a particle size distribution having a mean and/or median particle diameter of from 50 nm up to 5 μm are desirable to provide a high surface area material useful as a catalyst for hydrocracking and/or hydrotreating a crude oil or a crude oil fraction.